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PUV is the most common cause of severe types of urinary tract obstruction in children. It is thought to develop in the early stages of fetal development. The abnormality affects only males and occurs in about one in 8,000 births. This disorder is usually sporadic (occurs by chance). However, some cases have been seen in twins and siblings, suggesting a genetic component.



when the urethral valves partially impedes urine outflow. Reverse flow occurs and can affect all of the urinary tract organs including the urethra, bladder, ureters, and kidneys. The organs of the urinary tract become engorged with urine and swell, causing tissue and cell damage. The degree of urinary outflow obstruction will determine the severity of the urinary tract problems.

Posterior urethral valves (PUV) are obstructing membranous folds within the lumen of the posterior urethra that are caused by a still yet to be determined disruption in the normal embryologic development of the male urethra.

Posterior urethral valves
An oblique membrane associated with the verumontanum, the congenital obstructive posterior urethral membrane (COPUM), appears to be the cause of posterior urethral valves.

The pathogenesis of posterior urethral valves (PUV) appears to be due to an obstructing persistent urogenital membrane (figure 1). Although the exact mechanism resulting in this obstruction is not completely understood [4], it appears that the normal embryologic development of the male urethra between weeks 9 and 14 of gestation is disrupted.

Normal male urethral embryology — Between weeks four and six of gestation, the cloaca is divided into the anorectal canal and the urogenital sinus. Over the following weeks of gestation, the urogenital sinus is divided by the entrance of the mesonephric duct into the cephalad vesicourethral canal, giving rise to the bladder and pelvic urethra. The caudal portion of the urogenital sinus (genital tubercle) forms the phallic urethra. As the genital tubercle elongates in the male fetus, the urethral groove and folds are created. As the penile urethra grows, it moves towards the urethral plate of the glans penis. Complete fusion of the entire urethra occurs at about 14 weeks gestation.

PUV embryology — Several disruptions of the male embryologic urethral development have been proposed as the mechanism resulting in PUV [4]. These are based upon published anatomical descriptions in the literature and include the following [4]:

●Persistence of the urogenital membrane with abnormal canalization of the urethra.

●Overgrowth of urethrovaginal folds.

●Abnormal integration of the Wolffian duct into the posterior urethra. Normally, the insertion of the Wolffian duct occurs in the cloaca before its division into the urogenital sinuses and anorectal canal. The Wolffian duct then involutes into thin mucosal folds (plicae colliculi) that run distal and lateral to the verumontanum in the midprostatic urethra. In this proposed mechanism, PUV are thought to arise from abnormal anterior insertion of the Wolffian duct into the cloaca that results in a thicker, more prominent, fused, and obstructing fold.

CLASSIFICATION — The traditional classification for posterior urethral valves (PUV) was developed by Young in 1919 based upon autopsies of a case series of PUV as follows [5]:

●Type 1 valve − The most common form is composed of a ridge from the verumontanum that divides into two leaflets, which attaches to the anterior urethra (figure 1).

●Type 2 valve − This type of valve is no longer considered a form of PUV but is believed to be a dissection artifact. It was reported to extend from the verumontanum towards the internal sphincter and bladder neck.

●Type 3 valve − This form is a diaphragm distal to the verumontanum with a central perforation, which may be a result of an attempt to place an urethral catheter.

In the 1990s, this classification was challenged based upon anatomic evaluation of cases using radiologic studies and direct observation by cystoscopy [6-8]. This reassessment suggested that PUV are the result of a single pathologic condition of an oblique membrane associated with the verumontanum, which was defined as congenital obstructive posterior urethral membrane (COPUM). In this reevaluation, COPUM was differentiated from Cobb's collar, which is defined as a congenital urethral stricture caused by a transverse membrane in the posterior urethra, and which has no relationship with the verumontanum [9]. This new classification system has not yet been widely adopted into clinical practice.





●In the developed world, the vast majority of PUV cases are identified by prenatal ultrasonography. Prenatal ultrasonographic findings of bilateral hydronephrosis and a dilated bladder with a dilated posterior urethra (ie, keyhole sign) (image 1) in a male fetus is suggestive of PUV. (See 'Prenatal' above.)

●Patients who are diagnosed postnatally usually present either as a newborn with urinary tract symptoms, abdominal distension, or respiratory distress due to lung hypoplasia, or as a young infant with failure to thrive, urosepsis, poor urinary stream, or straining while voiding. Older boys may present with urinary tract infections, day time and nocturnal incontinence (enuresis), and symptoms of voiding dysfunction. (See 'Postnatal' above.)

●Clinical manifestations of the PUV include an increased risk of chronic kidney disease and bladder dysfunction. (See 'Renal and urologic manifestations' above.)

●The presumptive diagnosis of PUV is made by voiding cystourethrogram (VCUG) that demonstrates the hallmark findings of a dilated and elongated posterior urethra with a thin linear defect during the voiding phase (image 3 and image 4). Confirmation of the diagnosis is made by cystoscopy. (See 'Diagnosis' above.)





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Complications of Injecting Drug Use

  • Local problems—Abscess (Figures 240-2 
    Image not available.

    A 32-year-old woman with type 1 diabetes developed large abscesses all over her body secondary to injection of cocaine and heroin. Her back shows the large scars remaining after the healing of these abscesses. (Courtesy of ­Richard P. Usatine, MD.)

    and 240-3; Abscess), cellulitis, septic thrombophlebitis, local induration, necrotizing fasciitis, gas gangrene, pyomyositis, mycotic aneurysm, compartmental syndromes, and foreign bodies (e.g., broken needle parts) in local areas.2
    • IDUs are at higher risk of getting methicillin-resistant Staphylococcus aureus(MRSA) skin infections that the patient may think are spider bites (Figure 240-4).
    • Some IDUs give up trying to inject into their veins and put the cocaine directly into the skin. This causes local skin necrosis that produces round atrophic scars (Figure 240-5).
  • IDUs are at risk for contracting systemic infections, including HIV and hepatitis B or hepatitis C.
    • Injecting drug users are at risk of endocarditis, osteomyelitis (Figures 240-6and 240-7), and an abscess of the epidural region. These infections can lead to long hospitalizations for intravenous antibiotics. The endocarditis that occurs in IDUs involves the right-sided heart valves (see Chapter 50, Bacterial Endocarditis).2 They are also at risk of septic emboli to the lungs, group A β-hemolytic streptococcal septicemia, septic arthritis, and candidal and other fungal infections.


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Question 1 of 1

A 42-year-old African-American man has been diagnosed with hypertension for the past 10 years and treated with medication. One morning, he is found unresponsive by his wife. He is taken to the emergency department and pronounced dead by the physician. An autopsy revealed cardiac hypertrophy and a narrowing of the aorta just distal to the ligamentum arteriosum, with dilation of the intercostal artery's ostia. How could the death have possibly been prevented?



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